Object null reference exception when title is null

[dIeGoLi]

BreadcrumbTagHelper ExtractTitle throws an exception when the node title is null. Of course title should not be null, but in case that nodes are created dynamically from data, it could happen by mistake. In that case i would prefer the bread crumb node not to be visible instead of the complete page not working. What is your opinion on that? I could do a pull request for that.

Thanks for your effort in this library.